Summary of work: Compared with controls, elderly patients with late-onset depression without cognitive impairment and without "secondary depression," were found by PET to have globally increased brain glucose metabolism, but no regional increase compared with the global value. Neuropsychiatric rating scales were introduced to quantify behavioral abnormalities in aging and dementia, and to relate these to regional changes in brain metabolism as measured with PET. Behavioral changes are a major cause of institutionalization of AD patients.